An active group of NIH-funded investigators is requesting a new transmission electron microscope, a JEOL JEM-1230, to replace our current microscope, a 15-year-old JEOL 100CXII. Electron microscopy is an integral part of the research programs of the eight Major Users on this application, who have a collective total of 139 years of electron microscopy experience. A new, state-of-the-art instrument would meet these investigators' needs for technology available on recently-designed transmission electron microscopes that cannot be provided by any microscope currently housed on campus or in neighboring institutions. The proposed new microscope is much easier to use than our current JEOL 100CXII and has many features that will allow users to capture higher-quality images much faster. In addition, the new microscope provides capabilities, not found on our current electron microscope that meet investigator's needs for quantitative analysis. Specifically, the JEM- 1230 permits three kinds of on-screen measurements. Six Major Users must make more elaborate measurements. We propose, therefore, to insert a CCD camera, for which the JEM-1230 is properly constructed, that would allow for capture of digital images that can be imported directly into image analysis programs. Digital image capture would circumvent the current tedious and time-consuming task of developing standard negatives and then digitizing them for subsequent analysis. Acquisition of the JEM-1230 and accessory CCD camera would provide a significant technological improvement in our electron microscope facility and allow investigators to more rapidly and efficiently complete the Specific Aims of their research programs.